Method and device for cleaning deposited material from a molding surface of a mold for forming ophthalmic lenses

ABSTRACT

A method of cleaning deposited material from a molding surface (10) of a mold (1) for forming ophthalmic lenses, including bringing a cleaning head (20) into contact with the molding surface (10), the rotational axis (22) of the cleaning head (20) being arranged normal to the molding surface (10), rotating (220) the cleaning head (20) around the rotational axis (22) while maintaining the contact between the cleaning head (20) and the molding surface (10), moving the cleaning head (20) to perform a precession motion (110) around a central normal (11) on the molding surface (10), while rotating (220) the cleaning head (20) around the rotational axis (22) and while maintaining the contact between the cleaning head (20) and the molding surface (10). During the precession motion (110) the rotational axis (22) includes an inclination angle (α1,α2) with the central normal (11) on the molding surface (10).

This application is a divisional of U.S. patent application Ser. No.14/960,604, filed on Dec. 7, 2015, which claims the benefit under 35U.S.C. § 119 (e) of U.S. provisional application Ser. No. 62/088,833,filed on Dec. 8, 2014, each of which is herein incorporated by referencein its entirety.

FIELD

The invention relates to a method of cleaning deposited material from amolding surface of a mold for forming ophthalmic lenses, in particularcontact lenses. The invention also relates to a device for carrying outthe method.

BACKGROUND

It is known to produce ophthalmic lenses, in particular contact lensessuch as soft contact lenses, in an automated manufacturing process usingreusable molds. In mass production of contact lenses, specificallydisposable lenses which are worn only once and are then disposed of, ahigh number of contact lenses must be manufactured in a relatively shortperiod of time. In an embodiment of such process for the mass productionof soft contact lenses, a lens forming material, for example a polymeror prepolymer solution, is introduced into a female mold half, the moldis closed by the respective male mold half, and then the lens formingmaterial is polymerized and/or cross-linked with the aid of ultraviolet(UV) light to form the contact lens. The mold is subsequently opened andthe lens is removed from the male or female mold half of the openedmold. Suitable polymers formed by photochemical polymerization ofsuitable prepolymers include polymers based on polyvinyl alcohols (PVA)or silicone hydrogels (SiHy).

After removal of the lens from the male or female mold half, the maleand female mold halves are cleaned so as to remove any lens formingmaterial or other residues that may have deposited on the moldingsurface. During cleaning of the mold the molding surface is exposed to ajet of a cleaning liquid, which may comprise deionized water and/ororganic solvents, and is subsequently dried. However, despite thiscleaning process the deposits may not absolutely completely be removedfrom the molding surface. And although such minimal amounts of depositsmay accumulate on the molding surface over a considerable number ofproduction cycles they are so small that the contact lenses produced arewell within the specifications as regards their optical and geometricalproperties, so that these lenses are not detected as being defectiveduring optical inspection. The residues on the molding surface may be sosmall that over a considerable number of production cycles they may noteven be visible on the molding surfaces. However, as the number ofproduction cycles continues to grow the deposits on the molding surfacemay accumulate more and more until they may reach a level where thecontact lenses are detected as not being within the specificationsduring the inspection process. From that time, continuing production ofcontact lenses using this mold would lead to contact lenses which arerejected due to the lenses being outside the specifications.

Therefore, in order to obtain fault-free contact lenses which are wellwithin the specifications the deposits must be reliably removed from themolding surface on a regular basis, and in particular the deposits haveto be removed before they have accumulated to an amount where thecontact lenses produced from the mold having the accumulated deposits onits molding surface are detected as being defective. And while methodsfor abrasively cleaning these deposits from the reusable molds areavailable, such abrasive cleaning may result in the molding surface ofthe mold getting damaged, and this molding surface is a surface thatmust have optical quality and must be able to stand a high number ofproduction cycles. Since the reusable molds are very expensive, abrasionof the molding surface must be prevented while at the same time themolding surface must be reliably cleaned.

SUMMARY

It is therefore an object of the present invention to provide a methodand a device for reliably removing the deposits from the molding surfaceof an ophthalmic lens mold, in particular from the molding surface of acontact lens mold, without damaging the molding surface.

In order to overcome these problems, the present invention suggests amethod and a device as it is specified by the features of theindependent claim directed to the method and the device, respectively.Embodiments of the method and device according to the invention are thesubject matter of the dependent claims.

As regards the method, a method of cleaning molding surfaces of a moldfor forming ophthalmic lenses, in particular contact lenses fromdeposited lens forming material is suggested.

In particular, the invention provides a method of cleaning depositedmaterial from a molding surface of a mold for forming ophthalmic lenses,in particular contact lenses. The method involves bringing a cleaninghead having a rotational axis into contact with the molding surface, therotational axis of the cleaning head being arranged normal to themolding surface, and rotating the cleaning head around the rotationalaxis while maintaining the contact between the cleaning head and themolding surface. The cleaning head is moved to perform a precessionmotion around a central normal on the molding surface running throughthe apex thereof, while rotating the cleaning head around the rotationalaxis and while maintaining the contact between the cleaning head and themolding surface. During this precession motion, the rotational axis ofthe cleaning head includes an inclination angle with the central normalon the molding surface.

According to one aspect of the method according to the invention, theinclination angle is in the range of up to 40°, particularly in therange of up to 35° for a female and up to 25° for a male mold.

According to a further aspect of the method according to the invention,while being in contact with the molding surface the cleaning head ispressed against the molding surface using a force in the range of 10-20N, preferably a force of about 16 N.

According to still a further aspect of the method according to theinvention, the cleaning head is made of silicone.

According to yet a further aspect of the method according to theinvention, the cleaning head is made of a foamed material.

Still in accordance with a further aspect of the method according to theinvention, the cleaning head is covered with a cloth.

In accordance with another aspect of the method according to theinvention, the cleaning head has a concave or convex shape matching theconcave or convex shape of the molding surface.

Yet in accordance with another aspect of the method according to theinvention, the method further comprises the step of dispensing acleaning liquid onto the molding surface. In accordance with thisaspect, for example an amount of up to 300 μl of the cleaning liquid,preferably an amount of 50 μl to 200 μl for a female mold and 150 μl to300 μl for a male mold, is dispensed onto the molding surface.

In accordance with a further aspect of the method according to theinvention, the cleaning head is moved to perform the precession motionwith a rotational speed of 10 revolutions per minute to 300 revolutionsper minute around the central normal on the molding surface, preferablywith a rotational speed of 10 revolutions per minute to 100 revolutionsper minute, most preferably with a rotational speed of about 100revolutions per minute, and wherein the cleaning head is rotated aroundits rotational axis with a rotational speed of 10 revolutions per minuteto 300 revolutions per minute, preferably with a rotational speed of 50revolutions per minute to 300 revolutions per minute, most preferablywith a rotational speed of about 110 revolutions per minute.

In accordance with a still further aspect of the method according to theinvention, the molding surface is a convex molding surface, and thecleaning of the convex molding surface is started at an inclinationangle, preferably at an inclination angle of 25°. The inclination angleis then decreased stepwise until the rotational axis of the cleaninghead and the central normal on the molding surface coincide.

In accordance with another aspect of the method according to theinvention, the molding surface is a concave molding surface, and thecleaning of the concave molding surface is started with the rotationalaxis of the cleaning head and the central normal on the molding surfacecoinciding. The inclination angle is then increased stepwise, preferablyup to an inclination angle of 35°.

As regards the device for cleaning deposited material from a moldingsurface of a mold for forming ophthalmic lenses, in particular contactlenses, the device according to the invention comprises at least onecleaning head for cleaning deposited material from the molding surface.The cleaning head has a rotational axis. Additionally, the devicecomprises a positioning device for bringing the molding surface and thecleaning head in a predefined position relative to one another, in whicha central normal on the molding surface running through the apex thereofand the rotational axis of the cleaning head coincide. Furthermore, thedevice includes a tilting device for tilting the cleaning head such thatthe rotational axis of the cleaning head and the central normal on themolding surface include an inclination angle. The device furtherincludes a first drive for rotating the cleaning head around therotational axis, a second drive for moving the cleaning head to performa precession motion around the central normal on the molding surface,and a controller for controlling the position of the molding surface andof the cleaning head relative to one another, for controlling therotational speed of the cleaning head around the rotational axis, forcontrolling the rotational speed of the precession motion of thecleaning head around the central normal on the molding surface, and forcontrolling the inclination angle between the rotational axis and thecentral normal on the molding surface.

According to one aspect of the device according to the invention, thedevice further comprises a dispensing needle for dispensing a cleaningliquid onto the molding surface.

According to a further aspect of the device according to the invention,the cleaning head is mounted to a rotational support, and a cloth isattached to the rotational support so as to cover the cleaning head.

The afore-mentioned aspects of the method according to the inventionhave a number of advantages. One advantage is the reliable manufactureof ophthalmic lenses, in particular contact lenses, without any lensesbeing produced which are outside the specifications due to too muchdeposits having accumulated on the lens molding surface of the molds.Such deposits are removed before they have accumulated to an extent thatthey would lead to defective lenses being produced. The method may beeither performed in-line in a fully automated or semi-automated processfor forming ophthalmic lenses, or may be performed off-line separatefrom such fully automated or semi-automated process for formingophthalmic lenses. In the latter case, the reusable molds comprising themolding surfaces to be cleaned have to be removed from the automatedproduction line for being cleaned after a predetermined number ofproduction cycles (numbers of contact lenses produced using therespective reusable mold). For example, after 600 production cycles thereusable molds may be removed from the production line and may becleaned in accordance with the invention.

Cleaning of the molding surfaces may start with the rotational axis ofthe cleaning head coinciding with the central normal on the moldingsurface, or may start with these axes including an inclination angle.The inclination angle between the rotational axis of the cleaning headand the central normal on the molding surface running through the apexthereof may be increased or decreased stepwise, for example in steps of1° to 10°, preferably in steps of 5°. This ensures a complete andreliable cleaning of the entire molding surface. The cleaning time ateach inclination angle may for example be in the range of 10 seconds to300 seconds, more particularly in the range of 10 seconds to 30 seconds.

While being in contact with the molding surface, and in particularduring the rotational movement and the precession movement of thecleaning head, the cleaning head is preferably pressed against themolding surface with the predetermined force in the range specifiedabove which is sufficient on one hand to reliably remove the depositedmaterial from the lens forming surface while at the same time a force inthe said range prevents the molding surface of the mold from gettingdamaged.

The cleaning head is preferably made of silicone or a foamed material(for example polyurethane) which are particularly well suitable for thegentle removal of the deposited material from the molding surfacewithout abrasion of the molding surface of the mold.

The cleaning head may be covered by a cloth, for example a microfibercloth, which may lead to excellent results in the cleaning of themolding surface. The cloth also may provide for additional protection ofthe molding surface, while deposits removed from the molding surface maybe held back (entrapped) within the cloth structure.

The cleaning head may have a concave or convex shape matching theconcave or convex shape allowing for optimal cleaning conditions withminimal impact on the molding surface by evenly distributing thepressure applied to the surface of the cleaning head in contact with themolding surface, and also allows for an optimal use of the cleaning headsurface.

A cleaning liquid may optionally be added onto the molding surface, inparticular in case of persistent residues or to loosen the residuesbefore the mechanical cleaning process begins. The amount of cleaningliquid specified above may lead to an increased performance in thecleaning of the molding surface. The cleaning liquid may be, forexample, deionized water, alcohols, surfactants or mixtures thereof.

When the molding surface is a convex molding surface, cleaning of theconvex molding surface is advantageously started at an inclination angleof 25° between the rotational axis and the central normal onto themolding surface, and the inclination angle is then stepwise decreased,preferably in 5° steps, until the rotational axis of the cleaning headand the central normal on the molding surface coincide. Accordingly, theprecession movement starts at an inclination angle of 25°, and after apredetermined cleaning time (rotational movement and precession movementof the cleaning head at 25°) the rotational axis is then moved to aninclination angle of 20° at which cleaning is again performed for apredetermined cleaning time. Thereafter, the rotational axis is moved toan inclination angle of 15° at which cleaning is performed for apredetermined cleaning time, and so on. Thus, the rotational axis ismoved in steps of 5° towards the central normal on the convex moldingsurface.

When the molding surface is a concave molding surface, however, cleaningof the concave molding surface is advantageously started with therotational axis of the cleaning head and the central normal on themolding surface coinciding, and the inclination angle then increasedstepwise, preferably in 5° steps, until the rotational axis of thecleaning head and the central normal onto the molding surface include aninclination angle of 35°. This is performed in a similar manner as isdescribed in the preceding paragraph, however, in this case therotational axis is moved in steps of 5° away from the central normal onthe concave molding surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous aspects of the invention become apparent from thefollowing description of embodiments of the invention with the aid ofthe drawings in which:

FIG. 1 is a schematic representation showing components of a deviceaccording to the invention for cleaning the molding surface of a concavecontact lens mold, and

FIG. 2 is a schematic representation of similar components of a devicefor cleaning a convex contact lens mold.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a female mold 1 having a molding surface 10 to be cleaned,as well as components of a device according to one embodiment of theinvention. In particular, a cleaning member 2 comprising a cleaning head20 having a convex shape and a rotational support 21 is shown, withcleaning head 20 being attached to rotational support 21. Cleaning head20 (as well as cleaning member 2) has a rotational axis 22 and can berotated about this rotational axis 22. In addition, a cloth 23 isattached to rotational support 21 by means of a clamping ring 24 in amanner such that cloth 23 covers cleaning head 20. Cloth 23 can beremoved by removing clamping ring 24 in order to replace a used cloth orto replace the cloth actually attached to rotational support 21 with acloth having different properties than the one actually attached torotational support 21. Alternatively, molding surface 10 can be cleanedby cleaning head 2 without using a cloth 23 covering the cleaning head2. As can be seen from FIG. 1, cleaning head 20 has a convex shapematching concave shape of concave molding surface 10.

Generally, cleaning head 20 can be made of any material suitable forcleaning molding surface 10 without abrasion of molding surface 10. Anexample for such material is silicone, however, other materials aresuitable as well. For example, cleaning head 20 can be made of a foamedmaterial such as foamed polyurethane.

In addition, a tilting device is provided as is indicated bydouble-headed arrow 3 with the aid of which rotational support 21 aswell as cleaning head 20 can be tilted such that rotational axis 22 isinclined by an inclination angle relative to a central normal 11 runningthrough the apex (here: the lowermost point) of concave molding surface10. In FIG. 1, two such inclination angles α₁, α₂ are indicated by wayof example.

In addition, and a dispensing needle 4 is provided for dispensing acleaning liquid 40 into female mold 1. The cleaning liquid may be, forexample, deionized water, alcohols, surfactants or mixtures thereof.

A positioning device (not shown) is provided bringing molding surface 10of femal mold 1 and cleaning head 2 into a predefined position relativeto one another. In addition, a first drive is provided for rotatingrotational support 21 together witch cleaning head 20 about rotationalaxis 22, this being indicated by arrow 220 in FIG. 1. In addition, asecond drive is provided for moving the rotational support 21 togetherwith cleaning head 20 to perform a precession movement around thecentral normal 11 on the molding surface 10, this being indicated inFIG. 1 by arrow 110. Finally, a controller (now shown) is provided forcontrolling the position of the molding surface 10 and of the cleaninghead 20 relative to one another, for controlling the rotational speed ofthe precession motion of the cleaning head 20 around the central normal11 on the molding surface 10, and for controlling the inclination anglebetween the rotational axis 22 and the central normal 11 on the moldingsurface 10.

In the following, an embodiment is described how cleaning to the moldingsurface 10 of female mold 1 may be performed. First of all, rotationalaxis 22 of cleaning head 20 and the central normal 11 on concave moldingsurface 10 are brought into alignment such that they coincide, and thefirst drive rotates cleaning head 20 around the rotational axis with arotational speed of, for example, 110 rpm (revolutions per minute), asindicated by arrow 220. Cleaning head 20 is then moved towards concavemolding surface 10 and is brought into contact with molding surface 10in a manner such that it is pressed against molding surface 10 with apredetermined force of, for example, about 16N. In this relativeposition including no inclination angle between the central normal 11 onconcave molding surface 10 and rotational axis 22, cleaning is performedfor a period of, for example, 10 seconds.

Once this cleaning step is completed, the rotational axis 22 is tiltedrelative to the central normal 11 with the aid of the tilting device byan angle of 5°, so that the rotational axis 22 and the central normal 11now include an inclination angle of 5°. Rotation of the cleaning head 20around the (now inclined) rotational axis 21 is continued, however, inaddition to the rotation of the cleaning head 20 around the (inclined)rotational axis 22, the cleaning head is moved with the aid of thesecond drive such that the cleaning head 20 performs a precession motionaround the central normal 11, as this is indicated by arrow 110. Thisprecession motion around the central normal is performed with arotational speed of, for example, about 100 rpm (revolutions per minute)while at the same time the cleaning head is rotated around rotationalaxis 22 with a rotational speed of 110 rpm. The direction of theprecession movement around the central normal 11 on the molding surface10 and the direction of the rotation of the cleaning head 20 around therotational axis 22 are opposite to each other. Again, cleaning head 20may be pressed against molding surface 10 with a force F of about 16N,and cleaning is performed at this relative position for a period of, forexample, 10 seconds.

Once this cleaning step is completed, the rotational axis 22 is tiltedrelative to the central normal 11 with the aid of the tilting device by5° again, so that the rotational axis 21 and the central normal 11 nowinclude an inclination angle of 10°, and cleaning is performed in themanner already describe above. Thereafter, the inclination angle isincreased again by another 5°, and so on, until a final inclinationangle of 35° between the rotational axis 22 and the central normal 11 isreached, at which the last cleaning step is performed. Thereafter,cleaning head 20 can be retracted and female mold 1 with the cleanedmolding surface can be removed and returned to the production process.As has been mentioned above already, this cleaning method is suitable toremove persistent residues from molding surface 10 without causing anyabrasion of molding surface 10.

FIG. 2 shows another embodiment of the cleaning member 2 in which thecleaning head 20 has a concave shape in contrast to the embodiment ofthe cleaning head 20 shown in FIG. 1 which has a convex shape. However,the rest of the cleaning member may be identical to that alreadydescribed above with the aid of FIG. 1, so that it is referred to thecorresponding description above. It goes without saying that theembodiment of the cleaning member 2 comprising the cleaning head 20having the concave shape is particularly suitable for the cleaning ofthe molding surface of a male mold (having a convex shape of the moldingsurface).

Also, the process of cleaning the convex molding surface is similar tothe process already described above, so that it is referred to thecorresponding parts of the description above. However, in the case ofcleaning a male mold having a convex molding surface, the first cleaningstep is performed at an inclination angle of 25° between the rotationalaxis of the cleaning head and the central normal on the moldingssurface. Nevertheless, before being arranged to include the saidinclination angle of 25°, first of all the rotational axis and thecentral normal on the molding surface are aligned to coincide, and onlythereafter the tilting of the rotational axis to the inclination angleof 25° relative to the central normal is performed. Then, at theinclination angle of 25° the first cleaning step is performed. Once thiscleaning step is completed, the inclination angle is decreased by 5°,the next cleaning step is performed, etc., until the rotational axis andthe central normal on the moldings surface coincide. The last cleaningstep is then performed with the rotational axis and the central normalon the molding surface coinciding, and then the mold with the cleanedmolding surface is removed and returned to the production process.

As can be seen from FIG. 1 and FIG. 2, a flexible bellows-likeprotection sleeve 25 may be provided covering the moving parts ofcleaning member 2 so as to prevent that any particles or lubricant maycome into contact with the molding surface of the mold to be cleaned.

While the invention has been described with the aid of embodiments, itis evident for the person skilled in the art that various changes andalterations can be made without departing from the technical teachingunderlying the invention. Therefore, the invention is not intended to belimited to the described embodiments, but rather the scope of protectionis defined by the appended claims.

The invention claimed is:
 1. A device for cleaning deposited materialfrom a molding surface (10) of a mold (1) for forming ophthalmic lenses,in particular contact lenses, the device comprising: at least onecleaning head (20) for cleaning deposited lens forming material from themolding surface (10), the cleaning head (20) having a rotational axis(22), a positioning device for bringing the molding surface (10) and thecleaning head (20) in a predefined position relative to one another, inwhich a central normal (11) on the molding surface (10) running throughthe apex thereof and the rotational axis (22) of the cleaning head (20)coincide, a tilting device for tilting the cleaning head (20) such thatthe rotational axis (22) of the cleaning head (20) and the centralnormal (11) on the molding surface (10) include an inclination angle(α₁,α₂), a first drive for rotating (220) the cleaning head (20) aroundthe rotational axis (22), a second drive for moving the cleaning head(20) to perform a precession motion (110) around the central normal (11)on the molding surface (10), a controller for controlling the positionof the molding surface (10) and of the cleaning head (20) relative toone another, for controlling the rotational speed of the cleaning head(20) around the rotational axis, for controlling the rotational speed ofthe precession motion of the cleaning head (20) around the centralnormal (11) on the molding surface (10), and for controlling theinclination angle (α₁,α₂) between the rotational axis (22) and thecentral normal (11) on the molding surface (10).
 2. The device accordingto claim 1, wherein the device further comprises a dispensing needle (4)for dispensing a cleaning liquid (40) onto the molding surface (10). 3.The device according to claim 1, wherein the cleaning head (20) ismounted to a rotational support (21), and wherein a cloth (23) isattached to the rotational support (21) so as to cover the cleaning head(20).
 4. The device according to claim 1, wherein the cleaning head (20)is made of silicone or of a foamed material.
 5. The device according toclaim 2, wherein the cleaning head (20) is made of silicone or of afoamed material.
 6. The device according to claim 3, wherein thecleaning head (20) is made of silicone or of a foamed material.
 7. Thedevice according to claim 1, wherein the cleaning head (20) has aconcave or convex shape matching a convex or concave shape of themolding surface (10).
 8. The device according to claim 3, wherein thecleaning head (20) has a concave or convex shape matching a convex orconcave shape of the molding surface (10).